The invention relates generally to the field of communications systems, and more particularly to a communication link between a device such as a computer and a wireless modem linked to a data network.
Electronic mail (e-mail), voice mail and facsimile (FAX) have become very popular communications services. In providing such communications it is desirable to improve the mobility of the end user: i.e., to allow the user to connect to a data network anywhere, anytime, without wires or cables. It is also desirable to enable the user to easily send and receive e-mail, voice mail and video mail messages, and to receive "info-casts". Info-casts provide information such as stock quotes, weather forecasts, and sporting scores, and are commercially available through such companies as Pointcast.
An early solution to the challenge of enhancing user mobility included attaching an internal or external modem to a portable computer such as a lap-top computer. This solution required the user to locate a telephone jack or other cable connection, and then physically connect the computer to the data network by attaching a cable between the modem and the telephone jack. However, physically connecting the computer to the data network is not always possible or desirable.
More recently, wireless modems, usually in the form of a Personal Computer Memory Card International Association (PCMCIA) card, have been introduced to allow users access to the Internet via cellular and personal communication system (PCS) networks. In some cases technology such as Cellular Digital Packet Data (CDPD) is used. FIG. 1 illustrates a typical configuration of this kind.
In FIG. 1, a laptop computer 100 having an internal PCMCIA card (not shown) connects to an Internet service provider 140. The PCMCIA card is linked to a wireless network 110 via a wireless link 105. The network 110 can be, for example, a cellular or PCS network, and is linked to a Public Switched Telephone Network (PSTN) 130 via a link 120, and the PSTN 130 connects to the Internet service provider 140. This arrangement allows electronic messages to be transferred between the laptop computer 100 and the Internet service provider 140.
Automatic retrieval and batch transmission of queued e-mail or voice mail messages generated "off-line" using a portable computer (i.e., when the computer was not connected to the data network) with a PCMCIA wireless modem are commercially available. Text-to-speech technology allows the user to create voice mail messages by typing a message into the portable computer.
Commercially available systems can automatically transfer electronic messages by providing a software program for the laptop computer 100 that, when started, automatically checks for new mail if a connection to an Internet service provider has been established. The software can also be configured to automatically and periodically check for new mail according to a predetermined schedule.
Electronic messages can be sent immediately or queued for later sending when the user's terminal is in contact with the data network. For example, any unsent but queued messages can be sent the next time the program checks for incoming messages. The benefits of such features to the user include reduced tedium and greater convenience.
The primary shortcoming of PCMCIA wireless modems is that they reside inside the portable computer. Therefore, even if the user wants to send or receive only voice, he must carry around the portable computer. To overcome this difficulty, users have little choice but to buy a separate wireless phone.
Users who buy a separate wireless phone and wish to connect it to a computer encounter still other difficulties. The most common approach, a direct-connect cable between the computer and the phone, requires the user to manually connect the cable each time access to a wireless data service network is desired. IR links between a mobile phone and a portable computer such as a notebook computer are commercially available and partially overcome this difficulty. However, such links require a clear line of sight transmission path which is not always available or convenient.
Furthermore, commercially available solutions do not provide for automatic resynchronization and reestablishment or reactivation of the wireless link when the computer and the phone are brought within range of the wireless link after having been outside the range of the wireless link. Accordingly, commercially available solutions fail to transfer electronic messages as the computer and phone move in and out of range of the wireless link or each other.